In a discovery that could someday benefit people with traumatic brain injury, Alzheimer’s disease and schizophrenia, UT researchers have identified the properties of more than 100 memory-sensitive neurons that play a key role in how memories are recalled in the brain.
Bradley Lega, MD, professor of neurosurgery, neurology and psychiatry, said his findings, published in the magazine NeuroImage, may represent a novel deep brain stimulation therapy for other brain diseases and injuries.
It highlights the important question, ‘How do you know you are remembering something from the past versus trying something new that you are trying to remember? ” Peter O’Donnell Jr. Brain Institute.
The most significant finding was that firing occurred at a different time to other brain activity when memories were retrieved. This small difference in timing, called ‘phase compensation’, has not been reported in humans before. Together, these findings explain how the brain can “re-experience” an event, but also track whether the memory is something new or something that has been previously encoded.
“This is one of the clearest pieces of evidence to date showing us how the human brain works when it comes to remembering old memories versus creating new ones,” said Dr. Relieved.
His study identified 103 memory-sensitive neurons in the hippocampus and entorhinal cortex of the brain that increased their activity levels when memory coding was successful. The same pattern of activity returns when the patient tries to recall these same memories, especially very detailed memories.
This activity in the hippocampus may be relevant to schizophrenia because hippocampal dysfunction underlies the inability of schizophrenic patients to decode memories and hallucinations or delusions. Dr. Relieved said the neurons identified by Dr. Relief is an important piece of the puzzle as to why this is happening Carol Tamminga, MD, professor and president Psychiatry and Schizophrenia national expert.
“Hallucinations and delusions in people with psychotic illnesses are actual memories, processed by the nervous memory system as ‘normal’ memories, even if they are damaged. It is important to understand how the ‘phase shift’ mechanism is used to modify these memories,” said Dr Taminga. damaged”.
The opportunity to learn more about human memory arising from surgery in which electrodes are implanted into the brains of epilepsy patients could also be used to map disease episodes to identify neurons involved in memory. In the study, 27 electrode-mounted epilepsy patients at the US Southwestern University and Pennsylvania Hospital participated in a memory task to generate data for brain research.
Analysis of the data didn’t prove conclusively, but it did add new credence to an important memory model called Discrete Phases in Coding and Retrieval (SPEAR) that scientists developed from rodent studies.
“It was never nailed. Having a model is one thing. Another thing to show evidence that that’s what happens in humans,” said Dr. Relieved.
The SPEAR model, which predicts the “phase shift” mentioned in this study, was developed to explain how the brain can track new versus old experiences when it engages in memory retrieval. Previously, the only evidence supporting SPEAR came from rodent models.
Reference: Yoo HB, Umbach G, Lega B. Neurons in the human temporal lobe track multiple temporal contexts during episodic memory processing. NeuroImage. 2021; 245: 118689. doi: 10.1016 / j.neuroimage.2021.118689
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